Inflammatory cytokines inhibit upregulation of glycolipid expression by Schwann cells in vitro

Objective: To determine whether products of inflammatory cells can inhibit differentiation and synthesis of myelin glycolipids by Schwann cells. Background: Infiltration of the peripheral nervous system by inflammatory cells is a feature of acquired demyelinating neuropathies. It is not clear what role these cells have in causing demyelination or inhibiting myelin synthesis. Methods: Nonmyelinating rat Schwann cells were incubated with 1) different concentrations of activated supernatants (AS) from mitogen-activated inflammatory cells; 2) 8-bromo cyclic adenosine monophosphate (8Br cAMP), known to induce Schwann cell differentiation and synthesis of glycolipids; 3) 8Br cAMP and varying concentrations of AS; 4) 8Br cAMP and cytosine arabinoside (Ara Ci, which inhibits Schwann cell proliferation; 5) 8Br cAMP, AS, and Ara C; or 6) additional medium. Results: AS inhibits the capacity of cAMP to induce Schwann cell expression of myelin-associated glycolipids. Inhibition of glycolipid expression was independent of the capacity of these AS to induce Schwann cell proliferation. Conclusions: These data suggest that inflammatory mediators are capable of inhibition of Schwann cell differentiation and synthesis of myelin.